1. Field of the Invention
The present invention relates to valve return springs. More particularly it relates to a device which replaces conventional metal valve return springs with pneumatic spring returns. The device is suited for use on a wide variety of applications where metal return springs are conventionally employed to bias valves toward a first position opposing a mechanical or other force which moves the valves toward and to, a second position. The device is especially well suited for retrofiting conventional mechanical valve return spring assemblies used on internal combustion and other cycled engines. However, it would also serve well as an original equipment pneumatic valve return spring to replace conventional spring assemblies and provide a wide degree of utility and performance improvement in both the function and timing of such valve assemblies used on internal combustion and other engines employing valves for venting and/or intake.
2. Prior Art
Valve springs are widely used throughout the world on a wide variety of applications. Generally, the valve spring is used to bias the valve against an opposing force usually generated by a cam or valve actuating lever acting on the valve to force it toward, and to, a second or open position. The force provided by the valve return spring acts to return the valve to the first or closed position where the valve head is seated in a valve seat thus sealing the aperture inside the valve seat communicating with a chamber which is vented or filled through the aperture in the valve seat surrounding the valve head.
Such an arrangement is quite popular in the operation of internal combustion engines using gasoline, diesel, or similar combustive fuels where valve springs are conventionally used to bias intake and exhaust valves toward a first closed position by imparting a biasing force to counter the biasing force from a mechanical lever such as a valve lifter or cam lobe that imparts force on the actuating end of the valve to bias it toward a second or open position.
Conventional spring and valve assemblies suffer from a number of problems. One such problem is that of metal fatigue of the springs themselves which can cause them to break and the valve to fail with major mechanical failure consequences in engines turning at high revolutions. A second concern is that of valve timing which tends to be set by the mechanical cam or other device powering the valve lifter imparting force to the valve stem. In purely mechanical valve spring arrangements, varying the timing of the valves to achieve better fuel economy or engine performance is extremely complicated and unreliable and thus generally not worth the effort due to the potential consequences from an increased risk of failure of the valve system. Such purely mechanical valve spring systems also suffer from other maladies during high revolutions of the engine in that they tend to float or fail to close the valve quickly enough resulting in loss of performance and sometimes engine failure should the float be too extreme.
In an attempt to overcome such problems associated with mechanical spring systems, pneumatic or fluid actuated valve systems have been tried to provide the biasing means for such valves to resist the force imparted by the valve lever and return the valve to its seat once the cycle is complete. Pneumatic systems, using compressible gas, provide the ability to vary the force and timing of the valve closure and to overcome the shortcomings of mechanical spring valve biasing systems. Such pneumatic assemblies however, often require exotic dedicated cylinder head assembly machining utilizing drilled air supply distribution passages, integral valve return spring operating bores, complex valve stem seals, oiling arrangements, sealing bellows and sophisticated air control arrangements. Such exotic purpose-built or dedicated cylinder head valve operating systems remain largely unavailable due to the extreme costs involved with engineering, testing and manufacturing. All of these attempts add to the complexity and cost of a high performance competitive engine and tend to reduce the inherent reliability of the same. As a consequence, such pneumatic valve biasing assemblies are virtually impossible to use to retrofit the millions of existing internal combustion engines and are not cost effective when used as original equipment due to the major amount of machining and retooling required to implement the current complicated systems. However, various prior art has attempted to provide a pneumatic valve spring system suitable for use on internal combustion engines.
U.S. Pat. No. 4,592,313 (Speckhart) teaches a pneumatic valve return for intake or exhaust valves. Speckhart uses an upper piston attached to and acting on a valve stem when pressure from a pressurized gas supply is communicated to the upper piston. However, Speckhart is not easily retrofited to the millions of existing engines due to its interface with the valve. Also, Speckhart communicates the pressurized air in the pneumatic spring directly to the valve stem itself thereby causing sealing problems.
U.S. Pat. No. 5,586,529 (Vallve) discloses a pneumatic valve spring member that replaces the conventional valve spring. However, the dual donut or flexible baffle arrangement taught by Vallve would be unreliable in the high heat and friction environment encountered by valve springs in internal combustion engines.
U.S. Pat. No. 5,943,988 (Burger) teaches a gas change valve for internal combustion engines. However, Burger requires the use of an electromagnetic structure and a switching system in combination with an electro-pneumatic means for gas pressure. Burger is thus not an easy or desirable retrofit to existing vehicles and requires a complicated electromagnet system which would increase cost and would be prone to failure in the high heat and oily environment of engine valves.
U.S. Pat. No. 5,109,812 (Ericson) features a double pneumatic spring to translate a valve in both directions and eliminate the requirement for a valve actuating lever and/or cam. However, Ericson by design is not easily installed to retrofit existing valve springs on engines and even as original equipment would require a complete redesign of valve actuation in conventional internal combustion engines.
As such, there is a continuing need for improvement in valve biasing devices used to provide a force to bias valves which seal chambers to their closed or sealed position. Such a device should be simple in both operation and construction rendering it simple to install and maintain. Further, such a device should be easily installed as a retrofit to currently used valve springs on internal combustion engines in use today. Still further, such a device should be constructed to operate reliably in the high heat and oily environment of valve springs of internal combustion engines and should not easily fail.
The applicant""s device is an improved pneumatic valve return spring and system for operation, biasing force control, and operation thereof. The device in its simplest form to replace a conventional circular valve spring features a plurality of housings.
A static housing that is essentially donut shaped is mounted to a fixed position on a cylinder head wherein an aperture defined by an inner wall of the housing surrounds a conventional valve stem. An outer wall of the static housing, circumferentially parallel and substantially equally spaced from its inner wall, communicates with the inner wall on a bottom side and thereby defines a static housing chamber. An open side opposite the bottom side forms a static circular aperture communicating with the static housing chamber.
A dynamic housing, is shaped similar to the static housing also has an inner wall that surrounds a valve stem and is dimensioned for lateral engagement with the static housing. The inner wall is connected by a top wall to a circumferentially parallel outer wall equally spaced from the inner wall. A reciprocating chamber is defined by the inner wall, outer wall and top wall and communicates on an open side opposite the top side with a circular opening.
The circular opening of the dynamic housing is sized to accommodate the lateral translation of the reciprocating chamber over the inner and outer walls of the static housing with the reciprocating chamber in sealed communication with the static chamber using conventional seals such as O rings adjacent to the open side of the dynamic housing and the circular aperture of the static housing.
With the dynamic housing in operating position and engaged over the static housing, the two inner walls of both housings define a valve stem chamber that is sized to accommodate a valve stem therein and a valve guide if necessary. A biasing means such as a conventional coil spring surrounds the valve stem and biases the valve and dynamic housing attached to the distal end of the valve, toward a closed position. However, this biasing spring provides minimal biasing force only to maintain the dynamic housing in an elevated position when air pressure falls below a certain level.
The sealed engagement of the reciprocating chamber with the static chamber form an expansion chamber surrounding, but not communicating with, the valve stem. This expansion chamber will both contract and elongate when the dynamic housing reciprocates in its engagement over the static housing. Of course those skilled in the art will readily see that the dynamic chamber might also reciprocate into the static chamber by changing the inner and outer wall dimensions of both housings, and such is anticipated, however the current best mode of the device features the dynamic housing reciprocating over the static housing and the reciprocating chamber sized to translate over the inner and outer walls forming the static chamber.
In use, a pressurized air fluid supply would be communicated into the static chamber and would expand and thereby force the dynamic housing to translate away from the static housing by fluid pressure acting on the reciprocating chamber when communicated from its sealed engagement with the static chamber. This pressurized air supply would be provided by a pump or other means to provide a pressurized air supply to the static chamber through one or a plurality of conduits communicating in sealed engagement with the static chamber. When so communicated, the air pressure expands into the reciprocating chamber forcing the dynamic housing and attached valve away from the static housing thereby closing the valve into its seat and holding it there in biased engagement with a valve seat until the air pressure in the formed expansion chamber is vented using a means to vent the expansion chamber such as a conduit communicating therewith. Of course a valving means to open and close the conduit used to vent the expansion chamber as well as the conduit feeding pressurized gas to the static chamber would be used to time the pressurization and depressurization of the expansion chamber with the cycles of the engine to provide a means to time the opening and closing of the valve to its seat. Controlling these valves along with the amount of pressure forced into the static chamber when pressurizing it, would also provide a means for variable timing of the valve from its open position forced down by the cam or actuating lever, to its closed position with the valve head in the seat.
The air pressure inside the expansion chamber in this unique design is kept away from the valve stem and stem seals which seal the circumference of the valves and thus no modification is required as would be the case if this area was pressurized. Further, the reciprocating donut design allows for the device to easily be inserted in place of existing mechanical springs on conventional engines by placing the device in the spot where the original valve spring occupied and engaging it with the distal end of a valve in the conventional fashion. An optional oil drain passage provides a vent for any oil that would proceed past the valve seals.
It is therefor an object of this invention to provide a pneumatic spring device which is easily retrofitted in place of existing valve springs on internal combustion engines and other sites where such biasing valve springs are currently used.
Another objective of this invention is to provide such a pneumatic valve spring device which is simple in construction and installation and requires little or no modification to be inserted in place of conventional valve springs.
A further objective of this invention is to provide a pneumatic valve spring which lends itself to the elimination of valve float as well as being able to accommodate timing changes in the valve train cycle to increase engine power and/or economy.
An additional object of this invention is the provision of a pneumatic valve spring which is constructed to work in the high heat and oily environment of an internal combustion engine with great reliability.
Further objectives of this invention will be brought out in the following part of the specification, wherein detailed description is for the purpose of fully disclosing the invention without placing limitations thereon.